Ampmeter flickering

I would check your wiring for the gauges and under the dash. Pull the cluster out and look at the wires. I had this problem once and found that the main ammeter positive wire had melted sometime and had bare wire that would occasionally vibrate and ground to the dash frame. I rewired it with new wires and it never was an issue after that.

Make sure that you don't have any melted/exposed wires under your dash.